Place the eggs in a pot and cover them by an inch or so with cold water. Place over high heat and bring to a boil. Once it comes to a boil, turn the heat off, place a lid on the pan and let sit for 10 minutes.
Remove eggs from the hot water, and place in a boil of iced water. Let sit for 5 minutes. Peel.
Grate the eggs on a box grater or chop them with a knife.
In a large bowl, mix together the mayo, Greek yogurt, celery, mustard, salt and pepper. Taste for seasoning.
Gently fold in the shredded/chopped egg.
To serve, add lettuce to your bread or pita, then add the egg salad. Garnish with pickled red onions.